The present invention relates to an isoflavone enriched vegetable protein isolate and a process for producing the same.
Isoflavones occur in a variety of leguminous plants and oilseeds, including vegetable protein materials such as soybeans. These compounds, for purposes of the present invention, include daidzin, 6"-OAc daidzin, 6"-OMal daidzin, daidzein, genistin, 6"-OAc genistin, 6"-OMal genistin, genistein, glycitin, 6"-OMal glycitin, glycitein, biochanin A, and formononetin. As used herein, "Mal" represents "malonyl" and "Ac" represents "acetyl". The structures of these isoflavones are shown in Formulas 1 and 2 below. ##STR1##
______________________________________ Compound R.sub.1 R.sub.2 R.sub.3 R.sub.4 ______________________________________ Genistein OH H OH OH Daidzein OH H H OH Glycitein OH OCH.sub.3 H OH Biochanin A OH H OH OCH.sub.3 Formononetin OH H H OCH.sub.3 ______________________________________ ##STR2##
______________________________________ Compound R.sub.1 R.sub.2 R.sub.3 R.sub.4 ______________________________________ Genistin H H OH OH 6"-OMal genistin COCH.sub.2 CO.sub.2 H H OH OH 6"-OAc genistin COCH.sub.3 H OH OH Daidzin H H H OH 6"-OMal daidzin COCH.sub.2 CO.sub.2 H H H OH 6"-OAc daidzin COCH.sub.3 H H OH Glycitin H OCH.sub.3 H OH 6"-OMal glycitin COCH.sub.3 OCH.sub.3 H OH ______________________________________
It has recently been recognized that the isoflavones contained in vegetable proteins such as soybeans may inhibit the growth of human cancer cells, such as breast cancer cells and prostate cancer cells, as described in the following articles: "Genistein Inhibition of the Growth of Human Breast Cancer Cells: Independence from Estrogen Receptors and the Multi-Drug Resistance Gene" by Peterson and Barnes, Biochemical and Biophysical Research Communications, Vol. 179, No.1 p. 661-667, Aug. 30, 1991; Genistein and Biochanin A Inhibit the Growth of Human Prostate Cancer Cells but not Epidermal Growth Factor Receptor Tyrosine Autophosphorylation" by Peterson and Barnes, The Prostate 22: 335-345 (1993); and "Soybeans Inhibit Mammary Tumors in Models of Breast Cancer" by Barnes et al. Mutagens and Carcinogens in the Diet p. 239-253 (1990). These isoflavones also have been found to reduce cardiovascular risk factors, for example by reducing the levels of atherosclerosis inducing lipoproteins and low density cholesterol and by increasing endothelial dependent vasodilation response.
Typically these isoflavone compounds have been associated with an inherent, bitter flavor in vegetable protein materials such as soybeans. In the commercial production of such protein materials, such as protein isolates and protein concentrates, the focus has been to remove these isoflavone compounds.
In a typical conventional process for the production of a vegetable protein isolate, e.g. a soy protein isolate, a vegetable material containing protein is extracted with an aqueous alkaline extractant, typically having a pH of from about 8 to about 11, to extract protein from insoluble vegetable matter. The extractant preferably is relatively alkaline, usually having a pH of from about 9 to 10, since vegetable proteins are very soluble in extractants of higher alkalinity, leading to extraction of most of the protein from the vegetable material. The extractant containing the protein is separated from insoluble vegetable materials to provide a protein extract.
The protein isolate is then recovered from the protein extract. A protein material is precipitated from the extract by adjusting the pH of the extract to about the isoelectric point of the protein with a suitable acid. The precipitated protein material is then separated from the extract. Typically the protein material is separated from the extract at a temperature of from about 120.degree. F. to 150.degree. F. since the precipitated protein packs densely at these temperatures, enhancing the yield of the recovered protein material. Separation temperatures below 90.degree. F. are avoided since the protein becomes fluffy at such temperatures, reducing the yield and commercial usefulness of the recovered protein material. After the protein material is separated from the extract, the protein material is extensively washed to remove residual carbohydrates, isoflavones, ash, and other non-protein materials.
When the vegetable material contains isoflavones, in addition to protein, the isoflavones are solubilized by the aqueous extractant along with the protein. Much of the isoflavones remain solublized in the extract following separation of the precipitated protein material from the extract. After separation of the precipitated protein material from the extract, the extract and isoflavones solubilized therein are usually discarded. Residual isoflavones left in the separated protein material are usually removed by exhaustive washing of the protein material to ensure that the taste associated with the isoflavones is not present in the protein material.
It is desirable, however, to provide an isoflavone rich protein material, and a process for producing the same, which is suitable for administration in a diet. Such an isoflavone rich protein material can be used to provide the nutritional benefits of the protein and the health benefits of the isoflavones when administered in a diet.